The transcriptional repressor ID2 supports natural killer cell maturation by controlling TCF1 amplitude.

Gaining a mechanistic understanding of the expansion and maturation program of natural killer (NK) cells will provide opportunities for harnessing their inflammation-inducing and oncolytic capacity for therapeutic purposes. Here, we demonstrated that ID2, a transcriptional regulatory protein constitutively expressed in NK cells, supports NK cell effector maturation by controlling the amplitude and temporal dynamics of the transcription factor TCF1. TCF1 promotes immature NK cell expansion and restrains differentiation. The increased TCF1 expression in ID2-deficient NK cells arrests their maturation and alters cell surface receptor expression. Moreover, TCF1 limits NK cell functions, such as cytokine-induced IFN-γ production and the ability to clear metastatic melanoma in ID2-deficient NK cells. Our data demonstrate that ID2 sets a threshold for TCF1 during NK cell development, thus controlling the balance of immature and terminally differentiated cells that support future NK cell responses.

Runx2 (Runt-Related Transcription Factor 2) Links the DNA Damage Response to Osteogenic Reprogramming and Apoptosis of Vascular Smooth Muscle Cells.

[Figure: see text].

Combinatorial ETS1-dependent control of oncogenic NOTCH1 enhancers in T-cell leukemia.

Notch activation is highly prevalent among cancers, in particular T-cell acute lymphoblastic leukemia (T-ALL). However, the use of pan-Notch inhibitors to treat cancers has been hampered by adverse effects, particularly intestinal toxicities. To circumvent this barrier in T-ALL, we aimed to inhibit ETS1, a developmentally important T-cell transcription factor previously shown to co-bind Notch response elements. Using complementary genetic approaches in mouse models, we show that ablation of Ets1 leads to strong Notch-mediated suppressive effects on T-cell development and leukemogenesis, but milder intestinal effects than pan-Notch inhibitors. Mechanistically, genome-wide chromatin profiling studies demonstrate that Ets1 inactivation impairs recruitment of multiple Notch-associated factors and Notch-dependent activation of transcriptional elements controlling major Notch-driven oncogenic effector pathways. These results uncover previously unrecognized hierarchical heterogeneity of Notch-controlled genes and points to Ets1-mediated enucleation of Notch-Rbpj transcriptional complexes as a target for developing specific anti-Notch therapies in T-ALL that circumvent the barriers of pan-Notch inhibition.

Transcriptional regulation of natural killer cell development and maturation.

Natural killer cells are lymphocytes that respond rapidly to intracellular pathogens or cancer/stressed cells by producing pro-inflammatory cytokines or chemokines and by killing target cells through direct cytolysis. NK cells are distinct from B and T lymphocytes in that they become activated through a series of broadly expressed germ line encoded activating and inhibitory receptors or through the actions of inflammatory cytokines. They are the founding member of the innate lymphoid cell family, which mirror the functions of T lymphocytes, with NK cells being the innate counterpart to CD8 T lymphocytes. Despite the functional relationship between NK cells and CD8 T cells, the mechanisms controlling their specification, differentiation and maturation are distinct, with NK cells emerging from multipotent lymphoid progenitors in the bone marrow under the control of a unique transcriptional program. Over the past few years, substantial progress has been made in understanding the developmental pathways and the factors involved in generating mature and functional NK cells. NK cells have immense therapeutic potential and understanding how to acquire large numbers of functional cells and how to endow them with potent activity to control hematopoietic and non-hematopoietic malignancies and autoimmunity is a major clinical goal. In this review, we examine basic aspects of conventional NK cell development in mice and humans and discuss multiple transcription factors that are known to guide the development of these cells.

IL-17 signaling in steatotic hepatocytes and macrophages promotes hepatocellular carcinoma in alcohol-related liver disease.

BACKGROUND & AIMS: Chronic alcohol consumption is a leading risk factor for the development of hepatocellular carcinoma (HCC), which is associated with a marked increase in hepatic expression of pro-inflammatory IL-17A and its receptor IL-17RA. METHODS: Genetic deletion and pharmacological blocking were used to characterize the role of IL-17A/IL-17RA signaling in the pathogenesis of HCC in mouse models and human specimens. RESULTS: We demonstrate that the global deletion of the Il-17ra gene suppressed HCC in alcohol-fed diethylnitrosamine-challenged Il-17ra-/- and major urinary protein-urokinase-type plasminogen activator/Il-17ra-/- mice compared with wild-type mice. When the cell-specific role of IL-17RA signaling was examined, the development of HCC was decreased in both alcohol-fed Il-17raΔMΦ and Il-17raΔHep mice devoid of IL-17RA in myeloid cells and hepatocytes, but not in Il-17raΔHSC mice (deficient in IL-17RA in hepatic stellate cells). Deletion of Il-17ra in myeloid cells ameliorated tumorigenesis via suppression of pro-tumorigenic/inflammatory and pro-fibrogenic responses in alcohol-fed Il-17raΔMΦ mice. Remarkably, despite a normal inflammatory response, alcohol-fed Il-17raΔHep mice developed the fewest tumors (compared with Il-17raΔMΦ mice), with reduced steatosis and fibrosis. Steatotic IL-17RA-deficient hepatocytes downregulated the expression of Cxcl1 and other chemokines, exhibited a striking defect in tumor necrosis factor (TNF)/TNF receptor 1-dependent caspase-2-SREBP1/2-DHCR7-mediated cholesterol synthesis, and upregulated the production of antioxidant vitamin D3. The pharmacological blocking of IL-17A/Th-17 cells using anti-IL-12/IL-23 antibodies suppressed the progression of HCC (by 70%) in alcohol-fed mice, indicating that targeting IL-17 signaling might provide novel strategies for the treatment of alcohol-induced HCC. CONCLUSIONS: Overall, IL-17A is a tumor-promoting cytokine, which critically regulates alcohol-induced hepatic steatosis, inflammation, fibrosis, and HCC. LAY SUMMARY: IL-17A is a tumor-promoting cytokine, which critically regulates inflammatory responses in macrophages (Kupffer cells and bone-marrow-derived monocytes) and cholesterol synthesis in steatotic hepatocytes in an experimental model of alcohol-induced HCC. Therefore, IL-17A may be a potential therapeutic target for patients with alcohol-induced HCC.

Batf Pioneers the Reorganization of Chromatin in Developing Effector T Cells via Ets1-Dependent Recruitment of Ctcf.

The basic leucine zipper transcription factor activating transcription factor-like (Batf) contributes to transcriptional programming of multiple effector T cells and is required for T helper 17 (Th17) and T follicular helper (Tfh) cell development. Here, we examine mechanisms by which Batf initiates gene transcription in developing effector CD4 T cells. We find that, in addition to its pioneering function, Batf controls developmentally regulated recruitment of the architectural factor Ctcf to promote chromatin looping that is associated with lineage-specific gene transcription. The chromatin-organizing actions of Batf are largely dependent on Ets1, which appears to be indispensable for the Batf-dependent recruitment of Ctcf. Moreover, most of the Batf-dependent sites to which Ctcf is recruited lie outside of activating protein-1-interferon regulatory factor (Ap-1-Irf) composite elements (AICEs), indicating that direct involvement of Batf-Irf complexes is not required. These results identify a cooperative role for Batf, Ets1, and Ctcf in chromatin reorganization that underpins the transcriptional programming of effector T cells.

Poly(ADP-Ribose) Links the DNA Damage Response and Biomineralization.

Biomineralization of the extracellular matrix is an essential, regulated process. Inappropriate mineralization of bone and the vasculature has devastating effects on patient health, yet an integrated understanding of the chemical and cell biological processes that lead to mineral nucleation remains elusive. Here, we report that biomineralization of bone and the vasculature is associated with extracellular poly(ADP-ribose) synthesized by poly(ADP-ribose) polymerases in response to oxidative and/or DNA damage. We use ultrastructural methods to show poly(ADP-ribose) can form both calcified spherical particles, reminiscent of those found in vascular calcification, and biomimetically calcified collagen fibrils similar to bone. Importantly, inhibition of poly(ADP-ribose) biosynthesis in vitro and in vivo inhibits biomineralization, suggesting a therapeutic route for the treatment of vascular calcifications. We conclude that poly(ADP-ribose) plays a central chemical role in both pathological and physiological extracellular matrix calcification.

Murine thymic NK cells are distinct from ILC1s and have unique transcription factor requirements.

Group 1 innate lymphoid cells include natural killer (NK) cells and ILC1s, which mediate the response to intracellular pathogens. Thymic NK (tNK) cells were described with hybrid features of immature NK cells and ILC1 but whether these cells are related to NK cells or ILC1 has not been fully investigated. We report that murine tNK cells expressed the NK-cell associated transcription factor EOMES and developed independent of the essential ILC1 factor TBET, confirming their placement within the NK lineage. Moreover, tNK cells resemble NK cells rather than ILC1 in their requirements for the E protein transcription factor inhibitor ID2. We provide further insight into the mechanisms governing tNK-cell development by showing that the transcription factor ETS1 prevented tNK cell acquisition of the conventional NK-cell maturation markers CD11b and KLRG1. Our data reveal few ILC1 in the thymus and clarify the identity and developmental requirements of tNK cells.

A SUMO-acetyl switch in PXR biology.

Post-translational modification (PTM) of nuclear receptor superfamily members regulates various aspects of their biology to include sub-cellular localization, the repertoire of protein-binding partners, as well as their stability and mode of degradation. The nuclear receptor pregnane X receptor (PXR, NR1I2) is a master-regulator of the drug-inducible gene expression in liver and intestine. The PXR-mediated gene activation program is primarily recognized to increase drug metabolism, drug transport, and drug efflux pathways in these tissues. The activation of PXR also has important implications in significant human diseases including inflammatory bowel disease and cancer. Our recent investigations reveal that PXR is modified by multiple PTMs to include phosphorylation, SUMOylation, and ubiquitination. Using both primary cultures of hepatocytes and cell-based assays, we show here that PXR is modified through acetylation on lysine residues. Further, we show that increased acetylation of PXR stimulates its increased SUMO-modification to support active transcriptional suppression. Pharmacologic inhibition of lysine de-acetylation using trichostatin A (TSA) alters the sub-cellular localization of PXR in cultured hepatocytes, and also has a profound impact upon PXR transactivation capacity. Both the acetylation and SUMOylation status of the PXR protein is affected by its ability to associate with the lysine de-acetylating enzyme histone de-acetylase (HDAC)3 in a complex with silencing mediator of retinoic acid and thyroid hormone receptor (SMRT). Taken together, our data support a model in which a SUMO-acetyl 'switch' occurs such that acetylation of PXR likely stimulates SUMO-modification of PXR to promote the active repression of PXR-target gene expression. This article is part of a Special Issue entitled: Xenobiotic nuclear receptors: New Tricks for An Old Dog, edited by Dr. Wen Xie.

Reversibility of liver fibrosis.

Liver fibrosis is a serious health problem worldwide, which can be induced by a wide spectrum of chronic liver injuries. However, until today, there is no effective therapy available for liver fibrosis except the removal of underlying etiology or liver transplantation. Recent studies indicate that liver fibrosis is reversible when the causative agent(s) is removed. Understanding of mechanisms of liver fibrosis regression will lead to the identification of new therapeutic targets for liver fibrosis. This review summarizes recent research progress on mechanisms of reversibility of liver fibrosis. While most of the research has been focused on HSCs/myofibroblasts and inflammatory pathways, the crosstalk between different organs, various cell types and multiple signaling pathways should not be overlooked. Future studies that lead to fully understanding of the crosstalk between different cell types and the molecular mechanism underlying the reversibility of liver fibrosis will definitely give rise to new therapeutic strategies to treat liver fibrosis.

SUMOylation and Ubiquitylation Circuitry Controls Pregnane X Receptor Biology in Hepatocytes.

Several nuclear receptor (NR) superfamily members are known to be the molecular target of either the small ubiquitin-related modifier (SUMO) or ubiquitin-signaling pathways. However, little is currently known regarding how these two post-translational modifications interact to control NR biology. We show that SUMO and ubiquitin circuitry coordinately modifies the pregnane X receptor (PXR, NR1I2) to play a key role in regulating PXR protein stability, transactivation capacity, and transcriptional repression. The SUMOylation and ubiquitylation of PXR is increased in a ligand- and tumor necrosis factor alpha -: dependent manner in hepatocytes. The SUMO-E3 ligase enzymes protein inhibitor of activated signal transducer and activator of transcription-1 (STAT1) STAT-1 (PIAS1) and protein inhibitor of activated STAT Y (PIASy) drive high levels of PXR SUMOylation. Expression of protein inhibitor of activated stat 1 selectively increases SUMO(3)ylation as well as PXR-mediated induction of cytochrome P450, family 3, subfamily A and the xenobiotic response. The PIASy-mediated SUMO(1)ylation imparts a transcriptionally repressive function by ameliorating interaction of PXR with coactivator protein peroxisome proliferator-activated receptor gamma coactivator-1-alpha. The SUMO modification of PXR is effectively antagonized by the SUMO protease sentrin protease (SENP) 2, whereas SENP3 and SENP6 proteases are highly active in the removal of SUMO2/3 chains. The PIASy-mediated SUMO(1)ylation of PXR inhibits ubiquitin-mediated degradation of this important liver-enriched NR by the 26S proteasome. Our data reveal a working model that delineates the interactive role that these two post-translational modifications play in reconciling PXR-mediated gene activation of the xenobiotic response versus transcriptional repression of the proinflammatory response in hepatocytes. Taken together, our data reveal that the SUMOylation and ubiquitylation of the PXR interface in a fundamental manner directs its biologic function in the liver in response to xenobiotic or inflammatory stress.

Pregnane X receptor modulates the inflammatory response in primary cultures of hepatocytes.

Bacterial sepsis is characterized by a rapid increase in the expression of inflammatory mediators to initiate the acute phase response in liver. Inflammatory mediator release is counterbalanced by the coordinated expression of anti-inflammatory molecules such as interleukin 1 receptor antagonist (IL1-Ra) through time. This study determined whether activation of pregnane X receptor (PXR, NR1I2) alters the lipopolysaccharide (LPS)-inducible gene expression program in primary cultures of hepatocytes (PCHs). Preactivation of PXR for 24 hours in PCHs isolated from wild-type mice suppressed the subsequent LPS-inducible expression of the key inflammatory mediators interleukin 1ß (IL-1ß), interleukin 6 (IL-6), and tumor necrosis factor α (TNFα) but not in PCHs isolated from Pxr-null (PXR-knockout [KO]) mice. Basal expression of key inflammatory cytokines was elevated in PCHs from PXR-KO mice. Stimulation of PCHs from PXR-KO mice with LPS alone produced enhanced levels of IL-1ß when compared with wild-type mice. Experiments performed using PCHs from both humanized-PXR transgenic mice as well as human donors indicate that prolonged activation of PXR produces an increased secretion of IL1-Ra from cells through time. Our data reveal a working model that describes a pivotal role for PXR in both inhibiting as well as in resolving the inflammatory response in hepatocytes. Understanding the molecular details of how PXR is converted from a positive regulator of drug-metabolizing enzymes into a transcriptional suppressor of inflammation in liver will provide new pharmacologic strategies for modulating inflammatory-related diseases in the liver and intestine.

Regulation network and expression profiles of Epstein-Barr virus-encoded microRNAs and their potential target host genes in nasopharyngeal carcinomas.

Epstein-Barr virus (EBV) is associated with nasopharyngeal carcinoma (NPC) tumorigenesis. However, the mechanism(s) connecting EBV infection and NPC remain unclear. Recently, a new class of EBV microRNAs (miRNAs) has been described. To determine how EBV miRNAs control the expression of host genes, and to understand their potential role in NPC tumorigenesis, we profiled the expression of 44 mature EBV miRNAs and potential host genes in NPC and non-tumor nasopharyngeal epithelial tissues. We found that 40 EBV miRNAs from the BART transcript were highly expressed in NPC. Analysis of potential BART miRNA target genes revealed that 3140 genes and several important pathways might be involved in the carcinogenesis of NPC. A total of 105 genes with potential EBV miRNA binding sites were significantly downregulated, suggesting that EBV miRNAs may regulate these genes and contribute to NPC carcinogenesis. An EBV miRNA and host gene regulation network was generated to provide useful clues for validating of EBV miRNA functions in NPC tumorigenesis.